74 algebra De mystif ieD
• Perform addition and subtraction with decimal numbers. Add (or subtract)
two decimal numbers (or a whole number to a decimal number), by lining
up the decimal points, adding 0s behind the last digit if necessary. Once
this is done, perform the addition (or subtraction).
• Perform multiplication with decimal numbers. Multiply two decimal num-
bers (or a whole number and a decimal number), by carrying out the
multiplication as if the decimal points were not there. Once this is done,
count the total number of digits behind the decimal points and move the
decimal point to the left in the product number of places.
• Rewrite division problems containing decimal points as division problems
without decimal points. Divide two decimal numbers by rewriting the
quotient as a fraction and then clearing the decimal—that is, multiplying
the numerator and denominator by the same power of 10, large enough
to eliminate any decimal points.
In Chapter 7, some equations will contain decimal numbers. We will use
what we learned in this chapter to clear the equation of decimal points before
solving the equation.